Multiscale structure and band configuration tuning to achieve high thermoelectric properties in n-type PbS bulks

PbS shares several similar features with PbTe and PbSe, and it is much more earth-abundant and inexpensive, which is characteristic of promising Te/Se-free thermoelectric materials for intermediate temperature power generation. However, its thermal conductivity is much higher than those of PbTe and PbSe, which bring a big challenge for obtaining high-performance PbS. In this study, we rationally integrate multiscale structure involving point defects, nanoprecipitates, grain boundaries and dislocations in PbS by doping for decreasing lattice thermal conductivity and simultaneously tuning energy band configuration. Density functional theory (DFT) calculations demonstrate that the Cl-S-Sb-Pb defects with the lowest formation energy create an obvious shallow donor band and push upward-moving Fermi level, in good agreement with high electrical transport properties. Remarkably, PbS-0.067%PbCl2-1.5%Sb sample presents outstanding ZT of similar to 1.0 at 823 K and averaged ZT of similar to 0.62 at 423-823 K due to a low lattice thermal conductivity and a high power factor.